This invention relates in general to testing apparatus and deals more particularly with a method and apparatus for pretesting of the accuracy of the pressure indications obtained from pressure sensing blood vessel catheters.
Blood vessel catheters have long been used for monitoring internal bodily pressures so that the patient can be treated appropriately based on the pressure readings. For example, balloon-tipped catheters are used by inserting them into a peripheral vein and threading them through the right ventricle of the heart. Once the pressure sensitive end of the catheter has been properly positioned in this manner, its opposite end is connected to a transducer which produces electrical signals based on the pressures sensed by the catheter. The transduced signals are applied to a bedside monitor which displays a waveform providing a visual representation of the pressures sensed by the catheter.
Although the catheters are manufactured under stringent quality control standards, the accuracy of the pressure indications depends also on accurate calibration of the transducer and on proper operation of the bedside monitor in combination with one particular catheter and one particular transducer. Thus, if the transducer is calibrated inaccurately, as sometimes occurs, or if the overall combination is lacking in accuracy, the pressure readings will not be correct even if the catheter itself is of the highest quality. In the past, there has been no effective technique available for checking the accuracy of the overall assembly of components, and the inaccurate pressure readings that sometimes occur can lead to inappropriate treatment and other adverse consequences.
The present invention is directed to a method and apparatus for independently confirming the accuracy of a pressure sensing blood vessel catheter, as used in combination with a particular transducer and monitoring instrument, prior to insertion of the catheter into the body. In accordance with the invention, a testing syringe and plastic tube cooperate to provide an airtight test chamber. The syringe and tube are sterile and are equipped with a diaphragm through which the pressure sensitive end of the catheter can be extended into the test chamber. A plunger can be extended into the opposite end of the syringe barrel to apply pressure to the pressure sensitive end of the catheter. A calibrated scale imprinted on the syringe barrel gives an accurate pressure reading that can be compared with the pressure reading of the bedside monitor in order to asertain the accuracy of the assembly of pressure sensing equipment.